1. Field of the Invention
The present invention relates to a technology for printing images by jetting ink droplets from each of a plurality of nozzles to record dots on the surface of a printing medium, and particularly to a technology for inspecting whether or not ink droplets are jetted from the individual nozzles.
2. Discussion of the Background
An inkjet printer prints images by jetting ink droplets from a plurality of nozzles. The print head of an ink jet printer is equipped with a large number of nozzles. Due to an increase in ink viscosity and/or bubble entrainment and the like, some of the nozzles may clog and become incapable of jetting ink droplets. Nozzle clogging degrades image quality by causing dot dropout within the image.
The background way of inspecting for nozzle clogging is for the user to print a special test pattern on printing paper before starting the printing operation and to then examine the printed test pattern visually.
Most printers have a plurality of printing modes, including a high-image-quality print mode for achieving high image quality at a relatively high printing resolution and a high-speed print mode for achieving high-speed printing at a relatively low printing resolution. The importance of inspecting for dot dropout may vary with the print mode. In the high-image-quality print mode, for instance, inspection for dot dropout is important because the presence/absence of dot dropout markedly affects image quality. In the high-speed print mode, on the other hand, inspection for dot dropout is not so important because greater priority is given to speed than image quality.
Conventionally, the printer has conducted dot dropout inspection before the printing operation in response to an instruction from the user when the user thinks it necessary. Therefore, when nozzles have clogged and no dot dropout inspection is carried out before printing in the high-image-quality print mode, dot dropout may occur and make it impossible to obtain the desired image quality.
One object of the present invention is to provide novel technology enabling dot dropout inspection to be reliably effected when required.
A further object of the present invention is to overcome the above-noted problems of the background art.
In order to attain at least part of the above objects, in a first configuration of the present invention, different timings during a printing operation are preset, as timings for conducting an inspection for the presence/absence of jetting of ink droplets from nozzles, with respect to at least two print modes among a plurality of print modes. The plurality of print modes differ in at least one of print resolution and raster line recording speed indicative of the net time required to record one raster line. When printing is performed according to a print mode selected from among the at least two print modes, the inspection is conducted at the timing preset with respect to the selected print mode.
The need for dot dropout inspection differs according to print mode. Therefore, if the inspection is conducted at a timing matched to the print mode, reliable dot dropout inspection can be conducted as necessary.
In a second configuration of the present invention, different combinations of timings for conducting an inspection for the presence/absence of jetting of ink droplets from the nozzles and an inspection principle are preset with respect to at least two print modes among a plurality of print modes. The plurality of print modes differ in at least one of print resolution and raster line recording speed indicative of the net time required to record one raster line. When printing is performed according to a print mode selected from among the at least two print modes, the inspection is conducted in accordance with the timing and inspection principle preset with respect to the selected print mode.
Such an operation makes it possible to set a preferable combination of dot dropout inspection timing and inspection principle matched to the print mode, and thereby reliable dot dropout inspection can be conducted as necessary.
The printing may be performed without conducting the inspection in the print mode whose raster line recording speed and print resolution are lowest among all print modes usable by the printer. Since the necessity of dot dropout inspection is low in such a print mode, higher speed printing can be performed by not conducting dot dropout inspection.
Further, only nozzles actually used in the printing operation may be selected for targets of the inspection. This enables the inspection time to be shortened.
The present invention can be implemented in various modes including, for example, a dot drop inspection method and device, a computer program for realizing the functions of the method or device, a recording medium recorded with the computer program, and data signals including the computer program embodied in a carrier wave.